Title: Does seismic moment release process bear imprints of the nucleation mechanisms of deep earthquakes?
The generation of earthquakes at depths exceeding 60 km remains debated, as rocks at such depths are anticipated to be ductile. Seismological investigations have revealed a variety of rupture characteristics that are distinguishable between shallow (0–60 km), intermediate-depth (60–300 km) and deep-focus (300–700 km) earthquakes, and tend to attribute them to different nucleation mechanisms. Here, we apply machine learning classification to a global database of earthquakes with moderate to large moment magnitudes to show that depth-dependent elastic properties can explain the range of resulting rupture characteristics. We find that the rigidity of the surrounding medium is the primary control of almost all the depth-varying earthquakes’ source characteristics, suggesting that seismic moment release process bear few imprints of the nucleation mechanisms of deep and shallow earthquakes. Our results support a previously identified constant strain drop hypothesis, in which the ratio of coseismic slip to the characteristic rupture length remains largely unchanged for earthquakes at all depths and regardless of the nucleation mechanisms. These results also suggest that rigidity-corrected self-similarity holds for earthquakes of different depths and nucleation mechanisms.